The present disclosure relates to a semiconductor structure and a method of forming the same. More particularly, the present disclosure relates to methods to reduce metal void formation in an interconnect structure utilizing a gas cluster ion beam process as well as interconnect structures that are formed from the same.
Generally, semiconductor devices include a plurality of circuits which form an integrated circuit fabricated on a semiconductor substrate. A complex network of signal paths will normally be routed to connect the circuit elements distributed on the surface of the substrate. Efficient routing of these signals across the device requires formation of multilevel or multilayered schemes, such as, for example, single or dual damascene wiring structures. The wiring structure typically includes copper, Cu, since Cu based interconnects provide higher speed signal transmission between large numbers of transistors on a complex semiconductor chip as compared with aluminum, Al-based interconnects.
Within a typical interconnect structure, metal vias run perpendicular to the semiconductor substrate and metal lines run parallel to the semiconductor substrate. Further enhancement of the signal speed and reduction of signals in adjacent metal lines (known as “crosstalk”) are achieved in today's IC product chips by embedding the metal lines and metal vias (e.g., conductive features) in a dielectric material having a dielectric constant of less than silicon dioxide.
Metal voids in interconnect structures (including middle-of-the-line (MOL) and back-end-of-the-line (BEOL) structures) are a major performance, yield and potentially reliability detractor for 32 nm and smaller features. One major cause of the metal void is pinching off at the top of the openings (via/trench) by the diffusion barrier/adhesion liner/seed deposition processes which are typically performed using physical vapor deposition (PVD). Pinching will get significantly worse if the incoming profile is re-entrant. By “re-entrant” it is meant the diameter of the opening at the top of the via/trench is smaller than the remainder of the opening. Pinching will then affect the subsequent bulk metal fill leading to voids.
A need thus exists to provide interconnect structures in which metal voids are substantially reduced or totally eliminated therefrom.